bank 1

So I have 4 Sensors on my 03 Spyder GTS. Im trying to replace the Bank 1 Sensor 1. When I look up the parts it says front upstream sensor and rear upstream sensor. My question is which one is the correct sensor for the bank 1 sensor 1. The front manifold or the rear manifold one.

Get everyone, well after pulling a PO135, I got in a new oxygen sensor, and I see where the sensor is, but being as young as I am, I havent really ever taken apart this cars engine yet? What all needs to be taken out or done to replace the bank 1 sensor 1 02? I see it but cannot reach it...